5 Varieties of Piston-filler Brush Pens - Economy Pack The piston filler comes with a screw knob for easy loading; Rervoir in the handle to store water or ink when treval; Designed for kanji calligraphy and sumi painting, drawing and sketching; May also used for half pans, watercolor pencils, watersoluble crayons and pastels; Natural animal hair brush just like regular bamboo brushes.